1. Technical Field
This invention herein relates to a casting sand heating apparatus used in the foundry industry.
2. Background
Nowadays, there are two types of apparatus for heating sand. The first is a fluidized bed heating furnace, wherein the sand passing through the horizontal bed is fully covered by horizontal burning nozzles. In the furnace heat exchange is carried out between the sand and the flame at a high temperature so that the sand is heated. The efficiency of this heating device is low, it is less productive (3 metric tons per hour) and expensive. The total cost of this device is about $325,000, in China, and it is not acceptable for common manufactures. This type of heating apparatus has low efficiency, small capacity and high operating costs.
The second sand heating method is used by several Chinese manufactures. It burns gas, oil, or other energy source in a separate combustion chamber outside the furnace to generate high temperature air. The high temperature air is mixed with a certain amount of ambient air or recycled warm air to heat the sand in the heating apparatus. The temperature of the air produced from the above mentioned steps is lower than the temperature (500° C.) under which the furnace can withstand. In the furnace, two spiral lamina muddlers are arranged to mix the sand by revolving oppositely to carry out the heat exchange between the sand and the heated air. The whole apparatus is horizontal with one end for sand and heated air intake, and the other is for sand and surplus gas discharge. This type of apparatus can not meet the technical requirements of heating the sand up to 300° C.